Electrical measuring instrument



Jly 12, 1927.

Filed June 24. v1925 2 Sheets-Sheet 1 July 12, 1927. `1,635,595

E. F. wEsroN ET AL ELECTRICAL MEASURING INSTRUMENT Filed June 24, 1925 2 Sheets-Sheet 2 Patented July l2, 1927. l

UNITI-:o STATES 1,635,595 PATENT. OFFICE.-

EDWARD l'. WESTON AN D GRAN T CARPENTER, OI NEWARK, NEW JERSEY, ASSIGNOBS TO WESTON ELECTRICAL INSTRUMENT COBPORATIONOE WAVEEL'Y PAEK, NEW- ABI, NEW JERSEY, A CORPORATION F NEW JERSEY.

ELECTRICAL MEASURING INSTRUMENT.

.Application led June 24, 1925. Serial No. 39,362.

This invention relates to an electrical measuring instrument of the well known movable-coil type. j

The main object of the invention is a sim` pliication of the construction and arrangement of the parts of such an instrument whereby, .withoutsacrificing suicient accuracy, the cost of manufacture ismaterially cheapened.

One method byvwhich this object may be attained is by making the base of rigid insulating material, preferably of molded material, such as bakelite, which can be molded to exact dimensions, and so constructing l5 and arranging the parts that the base itself serves as the support or frame forholding the parts in proper allocation.

A featureof importance is the mounting of the soft iron core, about which the moving coil swings, on an insulating support eX- tending upwardly from the base plate and preferably formed as an integral part thereof.

The manner of securing the end of the lower spring to the moving coils is also a new feature in that this end of the spring is directly connected to the base. Still another feature of novelty is the mounting of the moving system on pivots one of which is located in the base itself, whilethe other pivot is carried by a member connected to the base and preferably formed integrally therewith, this member being preferably the insulating support which carries the core.

Still another feature of novelty is the con-v struction and arrangement of the permanent magnet, so that it can be readily removed without disturbing the moving systemz which thus becomes readily accessible for inspection and repair. Other features of novelty will appear from the following descrgio.

Referring tothe wings:

Fig. 1 is a plan of the instrument, drawn to about twice the Scale of the commercial device;

Fig. 2 is a similar plan with the case removed; l 5o Fig. 3 is a section on plane 3-3 of Fig. 2;

Fig. 4 is a perspective view of the permanent magnet; Fig. 5 is a perspective view of the base plate; v y

Fig. 6 is a detail showing the manner of mounting the permanent magnet; and

Fig. 7 isa section showing the bridge pieces molded into the base.

The permanent magnet 1, as shown in Fig. 4, is preferably made up of stamped steel plates, each of substantially annular 'form and having its ends so shaped as to form a cylindrical recess within which is mounted the moving system. The stamped out plates after hardening can be strongly and permanently 'magnetized No separate ole pieces are used, the ends of the laminas eing so shaped, as shown, to g surround the moving system. The laminas are held in assembled relation by means of fastening device 37 at the back and by nuts 35 and rings' or nuts 40 on the bolts 13 and 14, the bolts passing throu h openings 11' and 12 in the base plate ce Fig. 6) in which they are held in place by nuts 41. By removing the face plate and these nuts 41, the magnet as a whole may be removed bodily, thus leaving the moving system attached to the base but open for inspection and repair. This feature of construction we regard as new.

While it is preferred to use alaminated magnet, it may vbe desirable,'particularly in larger sizes of instruments, to use annular shaped bar magnets in which the pole pieces are machined out of the magnets, or attached thereto in any convenient manner.

The novelty of our invention mainly'resides in that'the base plate of molded insulating material, such as bakelite, is con-V structedand arranged to directly support most of the essential parts of the instrument. Necessity for separate electrical insulation of circuit connections is thereby avoided, and assemblage is greatly facilitated.

Thus, referring to Fig. 5, the base late 2 has molded therein the screwthreade pin 3 as 9 and 10,'for the main terminals, and 1 1v and 12 for thevbolts 13 and 14 supporting ermanent magnet: 'lfhe base is rabto receive the cylindrical metal casing which carries the glass cover.

The moving coil is provided at top and the ioo

bottom withjdpivot pins which b'ear on jewels carried by a justable screw members, 17, 18 the latter being mounted in the sleeve 8 and the former in a bridge member 19, carried 'by the pins 5- and 6. The sleeve 8 The core 20 is held in adjusted position by are carried the a screw pin .22.

The pointer 23 has the usual balancin arms 29 andis clamped to the movable co by suitable nuts on the upper pivot pin.

The ends of the mova e coils are electrically connected to ends of hair rings 24, 25 whose other ends are sec to abutments orv arms 26, 31. Theabutment 26 is securedto the spring washer 28, held against rotation by a tongue 42 (Fig. 1) extending into an opening in the bridge piece 19. The abutment 31 is secured to the terminal pin 7, molded into the base, and this means of anchoring the spring directly to the base is also a new feature.

The spring washers 27, 28, hold the `jewel-bearings in proper adjustment, the

spring washer 27 bein held'against rotation bya tongue exten ing into an opening in the base, as shown in Flg. 3.

The circuit connections are as follows from the terminal 30 to resistan coil 4, pin

7, arm 31, lower hairv spring 25, coil 16, up-

per hair sprin 24, bridge piece 19, connector 32 and t e second terminal 33.

It will be noted that throughout this circuit no insulation other than that aorded by the bese iteelf ie needed.

The base itself, constructed as described, constitutes the rigidframe on or in which ivotal supports for the moving coil and e softiron core, aswell as the locating means for positioning the permanent magnet, thereby affording means or readily and exactly locating the -I tial parts of the instrument.

It is also an im' rtant feature of the invention that it ma ves possible the manufacture of small-sized highgrade instruments (e. g. voltmeters) such as are now in radio sets, at low cost.

We claim:

1. In anl electrical measuring instrument, a base ofinsulating material, a permanent magnet'having adacent pole ieces, a movable 'coil pivoted tween sai pole pieces, and a stationary com supported in position required message within the coil by an upstanding portion of said base.

2. In an electrical measuring instrument, a base, a permanent magnet havin adjacent pole pieces, a movable coil pivote between said le pieces, and a stationa core supstandng portion of said base.

'3. In an electrical measurin instrument a base, a permanent magnet aving adjacent pole pieces and supported directl on said base and freely detachable there rom, a moving coil pivoted between said pole pieces, one of the pivot supports for said coil being located in the base and the other pivot support carried on a. bridge piece seporteoin position within the coi by an upcured to an upstanding portion of said base. l

4. An electrical measuring instrument as claimed in claim 3 havin a stationary core supported in position wit in the coil by an upstanding portion of said base.

5. In an electrical measuring instrument, a base of insulating material, a permanent magnet having ad'acent pole ieces, a mov-4 able coil pivoted etween sai ole ieces,

one of. the pivot su ports for sai coi being' located in the insu ating base and the other pivot support carried on a bridge piece secured to an upstanding portion'of said in sulating base.

6. An electrical measuring instrument as claimed in claim 5 havin a stationa core supported in position wit in the coil y an upstanding portion of said base.

7. In an electrical measuring instrument,-

a base of insulating material, a permanent magnet having adjcent pole pieces, a mov` tween sai able coil pivoted pole pieces,

one of the pivot supports for said coil be' ing located in the insulating base and the ot er pivot support carried on a bridge piece secured to an upstandinig portion of said insulating base, sprin or controlling the .movements of the coi one of said springs being anchored to the base of the mstru'- ment.

8. In an electrical measuring instrument a base, a permanent horse-shoe ma et su ported directly on said base 4and eely etachable therefrom and having spec VIl() ed 11s curved pole ieces, a moving system carried tached to said moving system, said needle and upper support bemg of less width than the gap between the e ieces, said moving systemj being of ess lameter than the curved space between the pole pieces, where" by the magnet and pole piecesmay-be removed without disturbingY the moving systeni.

on up r an lower supports independently4 of sai magnet upon said base, a needleat- 9. In an electrical measuring instrument a base of insulating material, a horse-slime.magnet carried by sai base and v:having integrally formed curved pole'pieces,

ermanent a movable :coil pivotal a ower support 'carried on abri sulatmg 1 ported in position between said l pole pivot support for-said coil mg located -m the base an upper pivot dgl, piece mma w l10. In an electrical Ymeasuringv instrument m a base of insulating material, 'a

horse-shoe ma having integr a. movable coil pivoted rmanent et carried by sa' base and y formed -curv pole ieces between i pole iec'es,a lower pivot support for said-coil Being located in the base an upper pivot support carried on a bridge piece secured to' an upstanding integral portion of said insulating base, and a stationary core supported in position within the coil by sald upstanding portion, the coil being provided 20 at its lower end with a control sprlng connected to the insulating base. f In testimony whereof, we. aix our signatures. i 1 i s EDWARD F. WESTN.

- `GRANT CARPENTER. 

